Electronic devices are being developed today at a dizzying rate. Everywhere you look, people are carrying cellular phones, compact disc (CD) players, personal digital assistants (PDAs), pagers, radios, MP3 players, and laptop computers. There is a problem with this proliferation of electronic devices, however: they seem to all use different power supplies with different connectors. Nothing is more frustrating than packing for a trip and having to leave your swimming suit at home because your suitcase is full with 4 different power supplies for your computer, PDA, phone and CD player.
There is a reason for the various power supplies and connectors. Each host device has different power requirements. For example, a laptop computer consumes much more energy than does a cellular phone. The extra power is needed to run motors like disk drives and CD-ROM players that the phone does not have. Additionally, the laptop may have to illuminate a 120 square inch screen continuously, while the cellular phone need only light a 4 square inch screen occasionally.
Another reason for the differing power supplies are the batteries associated with each device. Different rechargeable batteries have differing charging requirements. For example, a nickel-metal hydride battery may charge to a termination of 6 volts, while a Lithium-Ion battery can only be charged to 4.1 volts. If the lithium battery were charged with a nickel charger, the lithium battery could become “overcharged” when the voltage passed 4.1 volts. Under these conditions, lithium cells can release combustible gasses at high temperatures. This is known as thermal runaway and can greatly compromise battery performance.
One solution to the “multiple-device, multiple-power supply” problem is the multi-connector. Referring to FIG. 1, illustrated therein is a multi-prong adaptor 50 commonly available at electronics stores. Such an adapter 50 generally has several different prongs 10,20,30 coupled in parallel to a power cord 40. The power cord 40 may thus be connected to three different types of connections. The problem with such a device is that the power delivered by the supply is the same no matter what connection you are using. If the power supply is a 6 volt supply, you still can not charge a lithium battery with this connector (even if it does fit) because the battery may experience thermal runaway.
There is thus a need for a universal power supply capable of charging many different devices and battery types.